I guess RNG just wants me to continue playing arty. I try to get into the mindset to "enjoy playing arty" but I've got so many more interesting tanks to play right now that it feels like a chore but I do want the girl from it so can't help it.

That was in stock configuration with a 90% crew, only my third battle in that arty. Don't aim for direct hits, aim for the side to track and stun them with the splash. Look for bottlenecks where you might be able to stun multiple targets to make the most of each shot and be ready to relocate to make shots for yourself.

Obviously that works better if you get a team that shoot the tracked/stunned targets and I managed to get through most of the grind on the previous arty without getting one.

It's easy, completed it for the Obj.260 a few weeks back. Bought the M50/53 to do the mission, sold it when completed. However many games I have in it is how many attempts it took. I think it's about ~15 games or so...